J/A+A/679/A94 Six evolved stars in open clusters RVs (Delgado Mena+, 2023)
Planets around evolved intermediate-mass stars.
III: Planet candidates and long-term activity signals in six open clusters.
Delgado Mena E., Gomes da Silva J., Faria J.P., Santos N.C., Martins J.H.,
Tsantaki M., Mortier A., Sousa S.G., Lovis C.
<Astron. Astrophys. 679, A94 (2023)>
=2023A&A...679A..94D 2023A&A...679A..94D (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, open ; Stars, double and multiple ; Radial velocities ;
Optical
Keywords: planetary systems - stars: evolution -
planets and satellites: physical evolution -
open clusters and associations: general
Abstract:
We carried out a long-term campaign spanning 17 years to obtain
high-precision radial velocities (RVs) with the HARPS spectrograph for
a large sample of evolved stars in open clusters.
The aim of this work is to search for planets around evolved stars,
with a special focus on stars more massive than 2M☉ in light of
previous findings that show a drop in planet occurrence around stars
above this mass.
We used kima -- a package for Bayesian modelling of RV and activity
data with Gaussian process capability and Nested sampling for model
comparison -- to find the Keplerian orbits most capable of explaining
the periodic signals observed in RV data, which have semiamplitudes of
between 75 and 500m/s. We also studied the variation of stellar
activity indicators and photometry in order to discard stellar signals
mimicking the presence of planets.
We present a planet candidate in the open cluster NGC3680 that orbits
the 1.64M☉ star No. 41. The planet has a minimum mass of
5.13MJ and a period of 1155 days. We also present periodic and
large-amplitude RV signals of probable stellar origin in two more
massive stars (5.84 and 3.05M☉ in the clusters NGC2345 and
NGC3532). Finally, using new data, we revise the RV signals of the
three stars analysed in our previous paper. We confirm the stellar
origin of the signals observed in NGC2423 No. 3 and NGC4349 No. 127.
On the other hand, the new data collected for IC4651 No. 9122
(1.79M☉) seem to support the presence of a bona fide planet of
6.22MJ at a period of 744 days, although more data will be needed to
discard a possible correlation with the CCF-FWHM.
The targets presented in this work showcase the difficulties in
interpreting RV data for evolved massive stars. The use of several
activity indicators (CCF-FWHM, CCF-BIS, Halpha), photometry, and
long-term observations (covering several orbital and stellar
rotational periods)is required to discern the true nature of the
signals. However, in some cases, all this information is insufficient,
and the inclusion of additional data 'such as the determination of
magnetic field variability or RV points in the near-infrared' will
be necessary to identify the nature of the discovered signals.
Description:
Radial velocities and stellar activity indicators.
The RV survey on which this work is based is fully described in Paper
I (Lovis & Mayor, 2007A&A...472..657L 2007A&A...472..657L). The objects analysed in this
survey were first observed over a time-period of nearly 5 year (from
March 2005 to October 2009, ESO periods 75-83, PI: Lovis). In total,
142 stars were monitored within 17 open clusters using the HARPS
spectrograph at the ESO 3.6m telescope (R∼115000), and some of them
were also observed with CORALIE (1.2 m-Swiss Telescope, La Silla) in
previous years. For those stars showing large RV variations, we
collected more observations between March 2017 and March 2022 (ESO
periods 99-108, PI: Delgado Mena). In addition, we obtained a few RV
points for a number of stars in the ESO archive (periods 91-94, PI:
Alves, Canto-Martins). The RV values are provided in the online tables
associated with this publication. The observations were made in objA
mode (no simultaneous RV calibration) and the exposures times were
estimated in order to have individual spectra with a signal-to-noise
ratio (S/N) of at least ∼30 at ∼6000Å. This gives a typical RV
photon-noise of ∼3.5m/s, which is sufficient to detect massive planets
around the surveyed stars (with V magnitudes between 7 and 12).
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table2.dat 92 6 Gaia DR3 identification for each target
harps.dat 124 262 HARPS RV for 6 stars
coralie.dat 83 37 CORALIE RV for 2 stars
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Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 20 A20 --- Name Name
22- 23 I2 h RAh Simbad right ascension (J2000)
25- 26 I2 min RAm Simbad right ascension (J2000)
28- 32 F5.2 s RAs Simbad right ascension (J2000)
34 A1 --- DE- Simbad declination sign (J2000)
35- 36 I2 deg DEd Simbad declination (J2000)
38- 39 I2 arcmin DEm Simbad declination (J2000)
41- 44 F4.1 arcsec DEs Simbad declination (J2000)
46- 54 A9 --- --- [Gaia DR3]
55- 73 I19 --- GaiaDR3 Gaia DR3 source_id
75- 86 A12 --- SName Short name
88- 89 I2 --- NH Number of HARPS observations
91- 92 I2 --- NC ? Number of CORALIE observations
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Byte-by-byte Description of file: harps.dat
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Bytes Format Units Label Explanations
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1- 12 A12 --- SName Short name
14- 25 F12.6 JD BJD Date of observation (BJD-2400000)
27- 36 F10.6 km/s RV Radial velocity
39- 45 F7.5 km/s e_RV Error in RV
48- 55 F8.5 km/s FWHM CCF FWHM
59- 65 F7.5 km/s e_FWHM Error in CCF-FWHM
67- 74 F8.5 km/s BIS CCF bisector inverse slope
77- 84 F8.6 km/s e_BIS Error in CCF-BIS
87- 94 F8.6 --- Ha06 Hα index in Hα06 bandpass
97-104 F8.6 --- e_Ha06 Error in Ha06
107-114 F8.6 --- Ha16 Hα index in Hα16 bandpass
117-124 F8.6 --- e_Ha16 Error in Ha16
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Byte-by-byte Description of file: coralie.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 12 A12 --- SName Short name
14- 25 F12.6 JD BJD Date of observation (BJD-2400000)
28- 36 F9.6 km/s RV Radial Velocity
39- 45 F7.5 km/s e_RV Error in Radial Velocity
48- 54 F7.5 km/s FWHM CCF-FWHM
58- 64 F7.5 km/s e_FWHM Error in CCF-FWHM
66- 73 F8.5 km/s BIS CCF-BIS
76- 83 F8.6 km/s e_BIS Error in CCF-BIS
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Acknowledgements:
Elisa Delgado Mena, elisa.delgado(at)astro.up.pt
References:
Lovis & Mayor, Paper I 2007A&A...472..657L 2007A&A...472..657L
Delgado Mena et al., Paper II 2018A&A...619A...2D 2018A&A...619A...2D
(End) Patricia Vannier [CDS] 27-Sep-2023